refactor(transformer): replace URI with URL in HtmlTransformer

[marevol]

Summary

Replace java.net.URI with java.net.URL throughout HtmlTransformer to simplify URL resolution logic and remove now-redundant code.

Changes Made

• Replace URI-based URL resolution with URL-based resolution in storeData()
• Remove the deprecated getUrlFromTagAttribute(URL, ...) and addChildUrlFromTagAttribute(URL, ...) overloads that delegated to their URI counterparts
• Remove the complex fallback block in addChildUrlFromTagAttribute that manually reconstructed absolute URLs when URISyntaxException was thrown
• Handle /../-prefixed paths directly after URL resolution, which is the only edge case URL doesn't normalize automatically
• Swap URISyntaxException catch for MalformedURLException — cleaner and more precise

Testing

• Existing test suite covers URL resolution scenarios
• The removed fallback code handled the same cases that URL.resolve() now handles natively

Breaking Changes

• The protected getUrlFromTagAttribute(URI, ...) and addChildUrlFromTagAttribute(URI, ...) methods are removed. Any subclasses overriding those methods will need to migrate to the URL-based signatures.

Additional Notes

The previous implementation used URI as the primary type but kept URL wrappers marked @Deprecated, then added a large manual fallback when URISyntaxException was thrown. Since java.net.URL resolves relative references natively and the only gap (/../ normalization) is a small explicit check, the URI path is no longer needed.